This is an incredibly complicated subject full of dissenting opinions and obviously people have their preferences especially across different brew types. In my opinion, the effect of densification within grinders with longer, or multiple cutting paths is universally positive for flavor. Fine particles accumulate with eachother and with larger particles and everything is rolled and rounded. One of the things to remember is that over-grinding coffee, I assume you mean by putting it over and over through the same burr set, is not the same as putting it once through a longer burr set. With the cylindrical burrs, the coffee is doing the same thing that any other set of burrs do, only over a longer distance period of time, so the coffee has more time to densify.Below is a great James Hoffman video comparing traditional coffee grinders to roller grinders, though the company keeps a lot of the details a secret, their grinder not only has a very long grind path, but also a dedicated densification stage.
https://www.youtube.com/watch?v=WkYqHWThIpA
I have only done blind taste tests using my friends and family as unwitting participants, and they've universally preferred turbina over a 64mm flat burr grinder with titanium nitride burrs and a high-ish end conical hand grinder. But obviously, this may be a matter of preference!
MarkMarine|1 year ago